This invention relates to a dispersion feeder which is especially useful for automatically feeding product or articles to an automatic combination weighing machine of circular array type.
As disclosed, for example, in the opened Japanese patent specification No. 57-160021, the automatic combination weighing machine of circular array type has a plurality of weighing units arranged on a circumference at equal intervals and serves to selectively combine the weights of articles weighed simultaneously by the respective weighing units to obtain a total weight satisfying a predetermined condition. The dispersion feeder is located in the center of the circular array of the weighing units in order to disperse the articles fed to its central portion in the radial direction and supply them to weighing hoppers or preceding holding hoppers of the respective weighing units.
As described in the above Japanese opened specification, the dispersion feeder according to the prior art includes a generally conical or disc or dome-shaped central distributing member located in the center and a plurality of linear conveying troughs extending radially from the periphery of the central member to the respective weighing units. The central member is generally subjected to helical vibration by a vibrator attached to its bottom to uniformly distribute the articles fed by suitable means to its central portion successively toward its periphery. Each linear conveying trough is also subjected to linear slanting vibration by an individual vibrator attached thereto to convey the articles fed from the central distributing member to each corresponding weighing unit. Each weighing unit is unloaded automatically, when the weight of its content has participated in the above total weight of predetermined condition, that is, in an acceptable combination. In response to this unloading, the vibrator of the conveying through corresponding to this weighing unit is actuated for a pre-selected time to load said weighing unit with a substantially constant amount of articles.
As described above, each linear conveyer trough operates only for a predetermined time if the corresponding weighing unit has been unloaded, and otherwise is stopped, while the central distributing member operates always or along with each conveyor trough to shift the articles out of the periphery. Accordingly, the articles on the resting conveyer troughs may be pushed forward to result in excessive loading of the corresponding weighing units. Moreover, the articles may be supplied excessively onto the resting troughs to result in an increased thickness of the layer of articles which can cause excessive loading.
In the combination weighing machine, the amplitude of vibration of the central distributing member and the amplitude and duration of vibration of the conveyer troughs are previously adjusted so that an optimum amount of articles are supplied to each weighing unit in order to minimize the deviation of the resultant combined weight from the predetermined condition, that is, to improve the weigh-out accuracy. Therefore, such accidental excessive loading might reduce the weigh-out accuracy and has been a severe problem in the prior art.